Process for forming a plastic fill sheet on ocean floor silt

ABSTRACT

A resin solution is fed through an extrusion head disposed underwater and in close proximity to the sediment of the ocean floor. The solution is formed of a sea water insoluble resinplasticizer system dissolved in a sea water insoluble solvent, the resin-plasticizer system of the solution having a relatively high specific gravity greater than 1.0 so that, when the system precipitates in the sea water, it drops onto the sediment. Preferably, the extrusion head is moved along at a controlled rate to form a continuous sheet of a desired thickness.

United States Patent 9 [72] lnventor Thorndyke Roe, Jr,

Oxnard, Calif. [21] Appl. No. 864,222 [22] Filed Oct. 6, 1969 [45] Patented Mar. 23, 1971 v 73] Assignee The Ignited States of America as represented by the Secretary of the Navy [54] PROCESSFOR FORMING A PLASTIC FILL SHEET 0N OCEAN FLOOR SILT 2 Claims, No Drawings [52] U.S. Cl 61/36, 61/7 [51] Int. Cl E02b 3/12, E02b 29/06 [50] Field ofSearch 61/36, 1, 35; 116/295, 0.5; 260/334, 318

[5 6] References Cited UNITED STATES PATENTS 2,615,307 10/1952 Kjellman 6l/36X 3,236,671 2/1966 Dybalski et al. 61/36X 3,252,290 5/1966 Gagle et al 61/36 3,312,069 4/1967 Jorda 6l/36X 3,332,245 7/1967 Caron 61/36 3,359,738 12/1967 Dybalskietal. 61/36X 3,446,027 5/1969 Meijer 61/1X Primary Examiner-Stephen .I. Novosad Attorneys-R. S. Sciascia and Paul N. Critchlow PROCESS FOR FORMING A PLASTIC FILL SHEET ON OCEAN FLOOR SILT BACKGROUND OF THE INVENTION Thepresent invention relates to processes or techniques for settling loose or suspended sea floor sediment to improve underwater visibility. In particular, it relates to plastic films adapted for these purposes.

In many underwater operations, such as salvage operations or the more recently conducted Sealab tests, it is highly desirable to provide maximum visibility and, of course, loose sediment, such as is commonly found on the ocean floor, seriously restricts visibility when it is stirred into a suspended state. In such situations, it becomes necessary to wait until the sediment again settles and, since time is a critical factor in any underwater operations, the waiting period presents real problems. Various methods, such as the use of flocculating agents to settle the suspended sediments, have been attempted. However, although these agents are somewhat effective, once the settled material is disturbed, the waiting period still is required.

Another problem frequently experienced in underwater operations arises when the operator accidentally drops a hand tool or other oceanographic instruments onto the heavy layer of slit deposited on the ocean floor. Due to the weight of these objects, they become deeply imbedded in the silt and frequently are lost or, at least, require a substantialrecovery time.

BRIEF SUMMARY OF THE INVENTION The present invention minimizes the foregoing difficulties by forming a sediment-blauketing plastic film sheet directly on the loose sea floor sediment. To form the sheet, a solution formed of a sea water insoluble resin-plasticizer system dissolved in a sea water miscible solvent is extruded from a container through a submerged extrusion head directly onto the sediment. The resin system has a relatively high specific gravity so that the precipitate drops through the sea water onto the sediment and, to provide a continuous sheet, the extrusion head simply is moved along the sediment at a controlled rate. Typical formulations for the solution are set forth in the ensuing detailed description.

As already indicated, a primary object of the invention is to 'provide a means for forming continuous plastic sheet directly on loose sea floor sediment.

A related object is to form a sheet which becomes a flexible platform capable of supporting light loads as well as preventing loss of items accidentally dropped during underwater operations.

Another object is to form a sediment-blanketing sheet the strength of which increases with time.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION The apparatus used in carrying out the present process is not part of the present invention and, since it can be provided in a variety of well-known manners it would seem that the present invention is capable of being readily understoodwithout the need .of special drawings or illustrations. In general, the apparatus may include a reservoir for containing the film-forming solution and the reservoir should be connected to a dispensing head equipped with a shutoff valve and an extrusion slit. In carrying out the process the reservoir is filled with the solution and then submerged into close proximity with the sediment on the ocean floor. The valve is opened and the solution is permitted to escape through the extrusion slit. In actual practice, it will be found thatsome means for pressurizing the solution greatly facilitates the escape and, for this purpose, the reservoir may be coupled by a conduit to a type reservoir can be employed to make use of the compresble of covering the ocean floor sediment and preventing the sediment from becoming disturbed and suspended in the sea water. Also, this plastic film was found to have a strength sufficient to support light loads and a strength which increased with deposit'time:

Polyvinyl butyral resin 2 lb.

2-(2-ethoxyethoxy) ethanol 5 gal.

Chlorinated biphenyls- 26 lb.

Dibutyl phthalate 1 8 lb.

If desired, a dye such as Rhodamine B can be included in the formulation to render the deposited plastic sheet readily visible to the operator.

It is highly essential in formulating the solution to use a resin-plasticizer system which has a specific gravity greater than 1.0 and, preferably, a significantly greater than 1.0 so as to minimize any suspension of the plastic in the water. In other words, the precipitated resin plastic system must have a unit volume weight high enough to promote its dropping from the extrusion head onto the sea floor sediment. In the foregoing formulation, the plasticizer is incorporated to adequately increase the unit volume weight of the system, although, of course, the plasticizer also performs its customary function of rendering the film flexible.

The other significant factor in the formulation is the use of a solvent which itself is miscible and preferably soluble in sea water. Consequently, when the solution initially is exposed to the sea water, the solvent commences to dissolve in the sea water permitting the resin system to precipitate out in a desired manner. The initial film formed by the precipitation is sufficiently cohesive to provide a continuous sheet although,

.the present purposes although it certainly is conceivable that .other plasticizers would perform in the desired manner. Other representative solvents that can be used in lieu of the solvent identified in the formation are chloroethanol, dimethyl formamide and dimethyl sulfoxide. The substitute materials can be incorporated in approximately the same percentages used in the preferred formulation.

In any of these formulations, it is desirable to use sufficient solvent to permit a relatively free flow of the solution through the extrusion head. Too rapid formulation of the precipitate interferes with the extrusion and promotes clogging of the extrusion head. Other factors involved in the actual application of the film should be readily resolvable simply by trial and error procedures. For example, the thickness of the deposited film can be controlled by the rate of moving the extrusion head over the ocean floor.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than Efilli9l2 than 1.0 whereby the precipitate drops through the sea water onto the sediment. 2. The process of claim 1 wherein said solution consists essentially of the following formulation as expressed in parts by weight:

polyvinyl butyral resin 2 2-(2-ethoxyethoxy) ethanol 40 chlorinated biphenyls 26 dibutyl phthalate l8 

2. The process of claim 1 wherein said solution consists essentially of the following formulation as expressed in parts by weight: polyvinyl butyral resin 2 2-(2-ethoxyethoxy) ethanol 40 chlorinated biphenyls 26 dibutyl phthalate 18 